The IPC 610 does not require any wetting of solder on the solder destination side pad. All that is needed is 75% vertical fill of the PTH with 270 degree wetting lead to barrel for class 2 and 330 degrees for class 3.
Best Regards,
Jeff
Jeff Popp
Quality Assurance Technician
Compunetix
2420 Mosside Blvd.
Monroeville, PA 15146
(412) 858-6184
"Every right implies a responsibility; Every opportunity, an obligation, Every possession, a duty." ~ John D. Rockefeller
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Thursday, June 17, 2010 8:02 AM
To: [log in to unmask]
Subject: Re: [TN] Query on shelf life of PCBs & impact on solderability
Uppina,
Wow! LOTS of questions. I can only answer some.
1) Yes, generally ENIG boards store better than HASL boards. HASL board solderability decreases because of growth of oxide and growth of intermetallic. If the HASL layer is thin the intermetallic can reach the surface sooner and then, well, it ain't going to solder.
Vacuum packing can increase the shelf life of finishes that can oxidize. This assumes excellent packaging, not stored so long there are intermetallic problems, etc., etc.
For a lot more on this get the IPC series of docs on surface finishes. I can't remember the numbers, but I am sure someone else will respond with those.
2) Photos to TechNet get stripped out. Either sent to Steve Gregory or post on the IPC site.
Question to you: what IPC class of product are you building?
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Uppina Nagaraj
Sent: Thursday, June 17, 2010 7:30 AM
To: [log in to unmask]
Subject: [TN] Query on shelf life of PCBs & impact on solderability
Dear All,
I have 3 queries in all.....
1. One of our customer has changed the surface finish from HASL
to ENIG. Their main reason for this change was that they
have had a bad experience with storage of HASL finished boards
(the reason for which is not shared with us). They had encountered
solderability problems on the HASL finished board which they
had stored for a period of time.
Their expectation with Gold plated surface is the storage
of the PCBs can be for a longer period of time as compared to
HASL finish.
Initially they had a requirement for 1micron thick electrolytic gold,
but later on they changed the requirement for an ENIG process with
gold around 0.05 to 0.10 microns.
Now my question......
Is there any guideline on the shelf life of the PCBs (with regard to
solderability) of the following surface finishes....
a) ENIG
b) HASL
c) Immersion Tin
d) Electrolytic Ni and electrolytic gold with Gold thickness
of 1.0microns
Will vacuum packing help to extend the shelf life?
2. One of our customer is doing hand soldering of PCBs with ENIG finish.
They're inserting a strand of tinned Copper wires from component side
and later on using soldering iron to do the soldering from the solder
side.
The solder is able to flow up from solder side to component side, but
the solder is unable to complete wet the pad on the component side.
I've attached the photos of example of the phenomenon. These photos are
without the wire, I've just used bare PCBs to do the soldering to
illustrate the phenomenon.
Now my question....
a) Will increasing the volume of the solder help in complete wetting
of the pads on the component side?
b) Any other way to get a full coverage on the pads on the component
side.
3. This question is about the same customer which I've mentioned in
para 2 above, is doing hand soldering. In one of the stage of
component assembly, they're (hand) soldering a flexible PCB
on the ENIG finished rigid PCBs.
They have a unique practice during this stage of soldering. They've
explained to us that this particular component is very sensitive to
high temperature and hence the soldering iron temperature is set at
210Deg C. They're using Sn60/Pb40 solder for this soldering operation.
After the soldering iron achieves 210Deg C, they're turning off the
power to the soldering iron and doing the soldering of the flexi PCB
onto the rigi PCBs. We'll not know the actual
soldering iron temperature at the point of contact.
They've complained to us that the soldering is poor.
We know that the melting temperature of solder is around 183deg C. But,
is there any guideline on the minimum temperature for soldering to get
a good flow of solder and completely wetted solder?
Thanks for your inputs in advance.
Best Regards,
U.Nagaraj
MICROPACK Ltd,
Bangalore, INDIA.
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